The Cryosphere, 15, 1–24, 2021 https://doi.org/10.5194/tc-15-1-2021 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Geographic variation and temporal trends in ice phenology in Norwegian lakes during the period 1890–2020 Jan Henning L’Abée-Lund1, Leif Asbjørn Vøllestad2, John Edward Brittain1,3, Ånund Sigurd Kvambekk1, and Tord Solvang1 1Norwegian Water Resources and Energy Directorate, Box 5091 Majorstuen, 0301 Oslo, Norway 2Centre for Ecological and Evolutionary Synthesis, University of Oslo, Box 1066 Blindern, 0316 Oslo, Norway 3Natural History Museum, University of Oslo, Box 1072 Blindern, 0316 Oslo, Norway Correspondence: Jan Henning L’Abée-Lund (
[email protected]) Received: 21 December 2020 – Discussion started: 22 January 2021 Revised: 26 March 2021 – Accepted: 8 April 2021 – Published: Abstract. Long-term observations of ice phenology in lakes An understanding of the relationship between ice phenol- are ideal for studying climatic variation in time and space. ogy and geographical parameters is a prerequisite for pre- We used a large set of observations from 1890 to 2020 of dicting the potential future consequences of climate change the timing of freeze-up and break-up, and the length of ice- on ice phenology. Changes in ice phenology will have con- 5 free season, for 101 Norwegian lakes to elucidate variation sequences for the behaviour and life cycle dynamics of the 35 in ice phenology across time and space. The dataset of Nor- aquatic biota. wegian lakes is unusual, covering considerable variation in elevation (4–1401 m a.s.l.) and climate (from oceanic to con- tinental) within a substantial latitudinal and longitudinal gra- ◦ ◦ 10 dient (58.2–69.9 N, 4.9–30.2 E).